How to check for an undef value in a Matrix (in Julia) and assign a new value?

Question

I want to create a matrix A of undefined values and have the following code that works just fine.

A = Matrix{Tuple{Float64, Array{Int64, 1}}}(undef, 100, 100)

Later, I want to check if a particular cell is undefined and if so, assign a value after computing it. I tried isdefined(A, i, j) but that gave an error for too many arguments. How can I check for #undef and assign only if it is undefined?

The documentation on isdefined provides a method only for a single dimensional array, how do I achieve the same on a matrix?

Answer 1

Use isassigned:

julia> A[2,3]=(3.0, [])
(3.0, Any[])

julia> isassigned(A,2,3)
true

julia> isassigned(A,3,3)
false